buildman: Update default config to build for sandbox

At present the default .buildman file written by buildman does not specify
a default toolchain. Add an 'other' line so this works correctly and
sandbox builds run as expected.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/buildman/bsettings.py

@@ -74,6 +74,7 @@ def CreateBuildmanConfigFile(config_fname):
     print('''[toolchain]
 # name = path
 # e.g. x86 = /opt/gcc-4.6.3-nolibc/x86_64-linux
+other = /
 
 [toolchain-prefix]
 # name = path to prefix